Based on the fact that the human body is susceptible to cancer, several methods to decrease or eliminate the painful illness, or to discover cytotoxic substances have been proposed.
Although many chemotherapeutic agents are clinically useful for the treatment of several forms of cancer such as acute leukemia, Burkitt's lymphoma, retinoblastoma, Ewing's sarcoma, testicular carcinoma, choriocarcinoma, Hodgkin's disease, lymphosarcoma, rhabdomyosarcoma, or mycosis fungoides, they are inactive against human hepatoma.
Some natural .gamma.-pyrone compounds, Psorospermin (1) and related compounds, 3',4'-deoxy-psorospermin, 3',4'=deoxypsorospermin-3',4'-diol, 3',4'-deoxy-4'-chloropsorspermin-3'-ol, O.sup.5 -methyl-3',4'-deoxypsorospermin-3'-ol exhibit strong cytotoxic effects against leukemia cells (Habib, A. M. et al., 1987, J. Org. Chem. 52, 412-18). Recently Cushman, M. et al., reported the cytotoxicities of .gamma.-pyrone compounds, flavonoid analogues (J. Nat. Prod., 54, 1656-60, 1991). The inventors have also discovered more potent and selective antitumor agents, which are .gamma.-pyrone compound, cyclomorusin (2), cycloartomunin (3), dihydrocyclo-artomunin (4), artomunoxanth-otrione epoxide (7), dihydroisocycloartomunin (5), artomunoxanthone (6), cyclocommunol (8), cyclo-mulberrin (9), cyclocommunin (10) which were isolated and identified from the root bark of Formosan tripterospermum plants (Lin, C. N. et al., 1991, Phytochemistry, 30, 1669-1671; ibid, 1992, 31, 364-67, 2563-64, 2922-24), and have exhibited cytotoxic effects against human hepatoma PLC/PRF/5 and KB cells in vitro.
The name PLC/PRF/5 designates human primary liver cancer cells; the symbol KB designates epidermoid carcinoma cells.